there is MSY
they have really good prices for computer parts
and I also go to Computer Parts Land
they have descent prices and a pretty wide range

if you really don't want to build it yourself, for AU$70, MSY will build the PC for you from parts of your choice. the parts don't have to be from MSY, so you can shop around and try and get better prices on things.http://www.msy.com.au/SERVICES/Charge.htm